1. Field of the Invention
The present invention relates to a merocyanine dye and a photoelectric conversion device including a pair of electrodes and a photoelectric conversion section which is provided between the pair of electrodes and includes an organic photoelectric conversion layer.
2. Description of Related Art
Merocyanine dyes have been used for a wide range of applications because of their structural diversity and color tones. In particular, merocyanine dyes are useful as light absorption materials since they have highly selective absorption spectra and highly intense absorption spectra, and those having a wide variety of structures have been proposed in the field of silver-salt photography which utilizes their sensitizing powers. Among dyes of cyanine type, merocyanine dyes do not have any ion-pair structures, so they allow the making of organic electronics devices by vacuum evaporation. Applications of merocyanine dyes as organic electronics materials by taking advantage of such a property to photoelectric conversion devices are proposed in JP-A-2003-332551 and JP-A-2006-086160.
In fabrication of traditional visible-light sensors, photoelectric conversion devices are generally made, e.g., by forming PN junctions in semiconductors like Si. Widely used solid-state imaging devices are planar-array photoreceptors which each have photoelectric conversion devices placed in a two-dimensional array in a semiconductor and, in CCD or CMOS format, read out signals generated by photoelectric conversion in each photoelectric conversion device. However, those devices have problems that the aperture rates thereof decrease as they are made finer, and they require additional devices such as lenses. Although various suggestions have been made for improvements of those devices, drawbacks including low efficiency of light utilization still remain.
The method for overcoming such drawbacks is disclosed in JP-A-2003-332551, wherein photoelectric conversion devices are provided throughout the upper side of a readout circuit layer, light absorbed by the whole surface is converted into electric signals by the photoelectric conversion devices, and the electric signals are read out by the lower readout circuitry.
When organic dyes are used as photoelectric conversion materials, wavelength selectivity of their sensitivities that draws on their absorption selectivity is useful, and besides, it is possible to use them without color filters. So, organic dyes have advantages in cost and device performance. And it is also important that organic dyes have larger light absorption constants than inorganic photosensitive materials. From photosensitive layers made thinner by taking advantage of their larger light absorption constants, quality enhancement of light signals obtained can be expected.
Although JP-A-2006-086160, JP-A-2007-234650, Journal of Physical Chemistry, vol. 88, p. 923 (1984) are cited as the cases where merocyanine dyes are used in photoelectric conversion devices, the photoelectric conversion powers attained therein are not sufficient.